JPS6025497B2 - Non-tempered high tensile strength steel plate with low yield ratio - Google Patents

Description

【発明の詳細な説明】 この本発明は同一強度レベルの高張力鋼板に比して降状
比の低いポロン含有非調質高張力鋼板に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a poron-containing non-tempered high-strength steel plate that has a lower drop ratio than high-strength steel plates of the same strength level.

一般に降伏比の高い鋼は、伸びが４・さいために構造用
鋼として使用するとき、地震などに対して伸びが局部的
に集中して被断し易いために、土木建築の分野では歓迎
されない、そこで低降伏比鋼板としては抗張力８０ｋ９
／ゆで８５％以下、抗張力７０ｋ９′微で８０％以下、
また抗張力６０ｋ９′ゆで７５％以下のものが望まれる
。In general, steel with a high yield ratio has a low elongation of 4. When used as structural steel, the elongation is locally concentrated and easily fractured due to earthquakes, etc., so it is not welcomed in the field of civil engineering and construction. Therefore, as a low yield ratio steel plate, the tensile strength is 80k9.
/ 85% or less when boiled, 80% or less when tensile strength is 70k9' fine,
Further, it is desired that the tensile strength is 60k9' and 75% or less when boiled.

また暁入、暁もどしの調質処理をせずに圧延のま）、ま
たは圧延後競ならし処理を行なう鋼にＢ（ポロン）を添
加することはきわめて稀で、優に英国におけるｆｏｒｔ
ｉｗｅｌｄ鋼が知られているのみである。In addition, it is extremely rare to add B (poron) to steel that is rolled without heat-refining or refining, or that is subjected to conditioning treatment after rolling.
Only iweld steel is known.

Ｂは鋼中に固溶し、オーステナィト粒界に偏折した状態
で嘘入性を高めるが、Ｎと結合してＢＮを生成すればそ
の焼入性を消失する。B dissolves in steel and improves hardenability when it is polarized at austenite grain boundaries, but when it combines with N to produce BN, the hardenability disappears.

そこでスラブ加熱時に固袴Ｎ量が多いと厚板圧延後の冷
却過程でＢＮを生成して、その後の工程におけるＢの暁
入性向上効果がなくなる。たとえば、０．１５％Ｃ−０
．２５％Ｓｉ−１．６％Ｍｎ−０．２６％Ｍｏ−０．０
３％Ｎｂ−０．０５５％ＳｏＩＮ−０．００１％Ｂを基
本成分としＮ含有量を異にしたＡ鋼とＢ鋼のスラブを１
２５０ｑｏに加熱して圧延し、圧延のま）（放袷）の鋼
板×と、圧延後４５０００に３船ご保持して競もどし処
理した鋼板Ｙの抗張力ＴＳ、降伏点ＹＳ、降伏比ＹＲを
調べた結果は図面に示すとおりであるが、Ｎ含有量の多
いＡ鋼の強度はＮ含有量の少し・Ｂ鋼に比べ低いことが
わかる。Therefore, if the amount of solid N is large when heating the slab, BN will be generated during the cooling process after rolling the thick plate, and the effect of improving the incorporation of B in the subsequent process will be lost. For example, 0.15%C-0
．． 25%Si-1.6%Mn-0.26%Mo-0.0
1 slab of A steel and B steel with 3%Nb-0.055%SoIN-0.001%B as the basic components and different N contents.
Examine the tensile strength TS, yield point YS, and yield ratio YR of steel plate X heated and rolled to 250 qo, unrolled (unrolled), and steel plate Y held in three ships at 45,000 qo after rolling and subjected to competitive treatment. The results are shown in the drawings, and it can be seen that the strength of Steel A, which has a high N content, is lower than that of Steel B, which has a small N content.

この発明は以上のように基いて、鋼中に含有するＮを低
減することにより、鋼板圧延時にＢの暁入性向上効果を
発揮させてアシキュラーベーナィト組織とし、調質処理
をせずして使用できる低降伏比の高張力鋼板を提案する
ものである。Based on the above, the present invention reduces the N content in steel, thereby exhibiting the effect of improving the permeability of B during rolling of a steel plate to form an acicular bainite structure, without the need for heat treatment. This paper proposes a high-strength steel plate with a low yield ratio that can be used in

すなち、この発明はＣＯ．１１〜０．３５％、Ｓｉｏ．
０５〜０．９０％、Ｍｎｏ．７５〜２．５０％、Ｍｏｏ
．０５％以上０．４０％未満、Ｎｂｏ．０１〜０．０８
％、Ｓｏｌ山０．０３〜０．１５％、ＢＯ．０００２〜
０．００１５％、残部Ｆｅ及び不可避的不純物よりなり
、不純物中のＮを０．００３５％以下とした低降伏比の
非調質高張力鋼板である。That is, this invention is CO. 11-0.35%, Sio.
05-0.90%, Mno. 75-2.50%, Moo
．． 05% or more and less than 0.40%, Nbo. 01-0.08
%, Sol mountain 0.03-0.15%, BO. 0002～
0.0015%, the balance being Fe and unavoidable impurities, and is a low yield ratio non-heat treated high tensile strength steel sheet with N in the impurities being 0.0035% or less.

この発明ではＢとＮが重要な構成要件であり、発明者は
種々試験の結果上記成分範囲の鋼板が降伏比が０．６以
下の非調質高張力鋼板としてすぐれた機械的性質を有す
ることを確認した。In this invention, B and N are important constituent elements, and as a result of various tests, the inventor has found that a steel plate with the above composition range has excellent mechanical properties as a non-heat treated high tensile strength steel plate with a yield ratio of 0.6 or less. It was confirmed.

つぎに、この発明鋼板の成分範囲を限定した理由につい
て述べる。Next, the reason for limiting the range of components of the steel sheet of this invention will be described.

Ｃは、高張力鋼としての強度を確保するために必要な元
素で、０．１１％未満では機械的強度が得られない。C is an element necessary to ensure the strength of high-strength steel, and if it is less than 0.11%, mechanical strength cannot be obtained.

また０．３５％をこえて含有すると溶接性を阻害するの
で０．１１〜０．３５％が適当である。Ｓｉは強度の確
保と製鋼上の必要性から０．０５％未満にすることは好
ましくない。しかし０．９０％をこえた含有は鞠性を大
中に劣化させる。Ｍｎは０．７５％未満では所望の強度
と戦性を得るのが困難になる。Moreover, if the content exceeds 0.35%, weldability will be inhibited, so a content of 0.11 to 0.35% is appropriate. It is not preferable for Si to be less than 0.05% from the viewpoint of ensuring strength and necessity for steel manufacturing. However, if the content exceeds 0.90%, the ballability deteriorates during the course. If Mn is less than 0.75%, it becomes difficult to obtain the desired strength and fighting properties.

また２．５０％をこえた含有は異常組織を生起し、二枚
割れやラメラーティアの原因となり、溶接時にトラブル
を生じるので避くべきである。ＭｏはＢと共存したとき
暁ならし程度の遅い冷却速度での暁入性を高めるが０．
０５％未満は効果がなく、また０．４０％以上含有させ
てもそれ程の効果を生じない。Further, a content exceeding 2.50% should be avoided as it may cause an abnormal structure, causing splitting in two or lamellar tearing, and causing trouble during welding. When Mo coexists with B, it increases the dawning property at a cooling rate as slow as dawning, but 0.
If the content is less than 0.05%, there is no effect, and if the content is 0.40% or more, no significant effect will be produced.

Ｎｂは０．０１％以上の微量でも結晶粒を微細化し、低
温磁性を向上させるとともに、析出硬化によって強度を
上昇する。しかし０．０８％をこえると溶接性を劣化さ
せる。ＳｏＩＡＩは低温瓢性向上のため０．０３％以上
の含有量にするのが好ましい。Even in a trace amount of 0.01% or more, Nb refines crystal grains, improves low-temperature magnetism, and increases strength through precipitation hardening. However, if it exceeds 0.08%, weldability deteriorates. The content of SoIAI is preferably 0.03% or more in order to improve low-temperature melting properties.

しかし０．１５％をこえると鋼塊割れの原因になるので
避けるべきである。Ｂは廉価で入手できる元素であり、
必要強度を非調質状態で確保するためにも、本発明の主
要な構成元素である。すなわち０．０００２％以上の徴
量含有によって焼入‘性を高め強度を向上する。しかし
０．００１５％をこえると籾性を劣化するので、その含
有量は０．０００２〜０．００１５％を適当とする。ま
たＮの含有量はこの発明には極めて重要で、後記の実施
例からもわかるようにＢＮ生成を抑制しＢの糠入性を確
保するためその含有量を可及的少量に抑えるとともに、
後記実施例のように０．００３５％以下にすべきである
。上記成分組成よりなる鋼板は、熱間圧延後通常の放冷
処理、すなわち圧延のま）でベイナイト組織を呈して良
好な強度と鋤性と、さらに同一強度の高張力鋼板より、
低い降伏比を示す。However, if it exceeds 0.15%, it should be avoided as it may cause cracking of the steel ingot. B is an element that can be obtained at a low price,
It is also a main constituent element of the present invention in order to ensure the necessary strength in a non-tempered state. That is, by containing 0.0002% or more of features, hardenability and strength are improved. However, if it exceeds 0.0015%, rice quality deteriorates, so the appropriate content is 0.0002 to 0.0015%. In addition, the content of N is extremely important for this invention, and as can be seen from the examples below, in order to suppress the formation of BN and ensure the branability of B, the content is kept as small as possible, and
It should be 0.0035% or less as shown in the examples below. The steel sheet having the above composition exhibits a bainitic structure after hot rolling and then normal cooling treatment (i.e., until rolling), and has good strength and plowability, and also has better strength and plowability than a high-tensile steel sheet with the same strength.
Shows low yield ratio.

しかし、より高劉性を得るためにさらに焼もどし処理を
加えることは任意である。つぎに、この発明鋼の実施例
について説明する。However, it is optional to further add tempering treatment to obtain higher strength. Next, examples of this invention steel will be described.

第１表に示すこの発明の成分鋼（Ａ鋼、Ｂ鋼）とこの発
明に属さない比較鋼（Ｃ鋼、Ｄ鋼、Ｅ鋼）を溶製し、同
一条件で板厚１５肋の厚板鋼板に熱間圧延後、それぞれ
圧延のま）のものと、４５び０×０．批ｒの燐もどし処
理をしたものについて機械的試験をした。これらの結果
を第２表に示す。第１表 化学組成協 ※ 戊酸当量はＪＩＳ Ｇ−３１０１に示す次式による
炭酸師＝ｃ＋墨凶守十器十雫十＊十台協第２表 試験結
果 上記より明らかなように、本発明鋼は比較鋼より低い炭
素当量で高い引張り強さを示し、また同程度の引張り強
さでは低い降伏比であることがわかる。The component steels of this invention shown in Table 1 (A steel, B steel) and comparative steels not belonging to this invention (C steel, D steel, E steel) were melted and made into thick plates with a thickness of 15 ribs under the same conditions. After hot-rolling the steel plate, and 45 and 0×0. A mechanical test was conducted on the material that had undergone phosphor reversion treatment. These results are shown in Table 2. Table 1: Chemical Composition Association* The boric acid equivalent is calculated according to the following formula shown in JIS G-3101: carbonic acid = c + Sumikyoshojukijushizukuju * Judaikyo Table 2 Test results As is clear from the above, the present invention It can be seen that the steel exhibits higher tensile strength at a lower carbon equivalent than the comparison steel, and also a lower yield ratio at the same tensile strength.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図はＭｏ−Ｎｂ−Ｂ鋼におけるＮ含有量による抗張
力、降伏点、降伏比の比較図表である。FIG. 1 is a comparison chart of tensile strength, yield point, and yield ratio according to N content in Mo-Nb-B steel.

Claims (1)

【特許請求の範囲】[Claims] １ Ｃ ０．１１〜０．３５％、Ｓｉ ０．０５〜０．
９０％、Ｍｎ０．７５〜２．５０％、Ｍｏ ０．０５％
以上０．４０％未満、Ｎｂ０．０１〜０．０８％、ｓｏ
ｌＡｌ ０．０３〜０．１５％、Ｂ ０．０００２〜０
．００１５％、残部Ｆｅ及び不可避的不純物よりなり、
不純物中のＮが０．００３５％以下であることを特徴と
する低降伏比の非調質高張力鋼板。1C 0.11-0.35%, Si 0.05-0.
90%, Mn 0.75-2.50%, Mo 0.05%
0.40% or more, Nb0.01-0.08%, so
lAl 0.03-0.15%, B 0.0002-0
．． 0015%, the balance consisting of Fe and unavoidable impurities,
A non-heat treated high tensile strength steel sheet with a low yield ratio, characterized in that N in impurities is 0.0035% or less.